Basic UkmService implementation

components/ukm/observers/history_delete_observer.cc

Index: components/ukm/observers/history_delete_observer.cc
diff --git a/components/ukm/observers/history_delete_observer.cc b/components/ukm/observers/history_delete_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6a82e127f35c605fa3bf5c18d095eb445965b762
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+++ b/components/ukm/observers/history_delete_observer.cc
@@ -0,0 +1,43 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/ukm/observers/history_delete_observer.h"
+
+#include "components/history/core/browser/history_service.h"
+
+namespace ukm {
+
+HistoryDeleteObserver::HistoryDeleteObserver() = default;
+
+HistoryDeleteObserver::~HistoryDeleteObserver() {
+  for (history::HistoryService* history_service : observed_history_services_) {
+    history_service->RemoveObserver(this);
+  }
+}
+
+void HistoryDeleteObserver::ObserveServiceForDeletions(
+    history::HistoryService* history_service) {
+  if (history_service) {
+    history_service->AddObserver(this);
+    observed_history_services_.insert(history_service);
+  }
+}
+
+void HistoryDeleteObserver::OnURLsDeleted(
+    history::HistoryService* history_service,
+    bool all_history,
+    bool expired,
+    const history::URLRows& deleted_rows,
+    const std::set<GURL>& favicon_urls) {
+  if (!expired)
+    OnHistoryDeleted();
+}
+
+void HistoryDeleteObserver::HistoryServiceBeingDeleted(
+    history::HistoryService* history_service) {
+  history_service->RemoveObserver(this);
+  observed_history_services_.erase(history_service);
+}
+
+}  // namespace ukm